The importance of the self-interaction correction for Jahn–Teller distortion of the zinc vacancy in ZnGeP2

A cluster model is used to investigate the zinc vacancy in zinc germanium diphosphide in unrestricted Hartree–Fock method and density functional theory (DFT) with the B3LYP functional. While DFT maintains the symmetry of the defect, Hartree–Fock method, which is self-interaction free, predicts a symmetry breaking with the defect electron localizing on a single P atom instead of being equally spread over the four neighboring P atoms. While this distortion does not yet agree with the experimental observation of a pairing of P atoms, it illustrates the importance of the self-interaction and the difficulty in identifying the true minimum energy configuration of point defects in semiconductors.